Though, I have to say my original question was directed to the specific nature of the patchwork quilt nature of the bubbles only......I think it still needs answering....whereas in this case, it's regarding the difference in the shade of the bubbles against the colour of the actual drink.

Anyway, notice how wonderfully light in tone and hue the head of the ready-to-be-imbibed drink is ?

Why's that then ?..the drink is black !!.the head is white !!..

I believe the explanation is that the bubbles are very small (made with nitrogen) and so scatter light everywhere hence mostly white.

"Not everything in black and white makes sense"

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"It has been said that the primary function of schools is to impart enough facts to make children stop asking questions. Some, with whom the schools do not succeed, become scientists." - Schmidt-Nielsen "Memoirs of a curious scientist"

9. How does Guinness have a white head when the drink itself is treacly black?The answer, according to the New Scientist, is down to the bubbles which form the creamy top of the pint. These uniform-sized spherical bubbles, which rise from the black liquid, sit in a dense concentration at the top of the glass. Because they hold only air, they act in an opposite way to a magnifying glass, disseminating light. So light entering the foam is rapidly scattered, some of it finding its way back to the surface, appearing white. It's called Mie Scattering.

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9. How does Guinness have a white head when the drink itself is treacly black?The answer, according to the New Scientist, is down to the bubbles which form the creamy top of the pint. These uniform-sized spherical bubbles, which rise from the black liquid, sit in a dense concentration at the top of the glass. Because they hold only air, they act in an opposite way to a magnifying glass, disseminating light. So light entering the foam is rapidly scattered, some of it finding its way back to the surface, appearing white. It's called Mie Scattering.

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The head on a guiness is cream coloured not white, it appears stout produces a bubble which does not reflect light at the same intensity as larger.

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What am I doing thinking about science?

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